Attenuators for adjusting the output power of high-frequency signal sources such as signal generators are known in extremely diverse embodiments. The throughput attenuation of an attenuator of this kind can be adjusted within a broad dynamic range through a stepwise connection and disconnection of attenuation elements. The individual attenuation elements are connected to T networks or Pi networks by changeover switches, which are realized as electronic switches in modern equipment. Attenuators of this kind, which can be switched by means of electronic switches such as PIN diodes or transistors, for example, gallium arsenide MESFET transistors, are referred to as electronic attenuators.
Published German patent application DE 100 63 999, for example, discloses such an electronic attenuator.
The advantage of such electronic attenuators is in the faster switching speed and a substantially lower dependence of the operating life upon the number of switching cycles by comparison with attenuators with mechanical switching relays. One disadvantage of electronic attenuators, however, is their relatively high insertion loss (minimum attenuation, fundamental attenuation), for example, up to 5 dB, and their reduced linearity. Furthermore, the maximum output power is lower than with mechanical attenuators with mechanical changeover switches.